1. Field of the Invention
The invention relates to an improvement for moving carriages needing increased traction on any number of surfaces, and particularly for a self-propelled pool cleaner transported on a rotating wheel assembly which is required to climb vertical walls of pools which are composed of different surfaces.
2. Description of the Related Art
Swimming pools provide a wide variety of benefits and pleasures. There are countless varieties of swimming pools of widely varying size and design in place in parks, recreational facilities, schools, and homes. However, pools must be regularly maintained to keep the pool clean from dirt, sand and other debris which invariably find their way into the pool.
All manner of debris can be carried or blown into the pool and generally such debris settles to the bottom or onto the walls of the pool, where it will accumulate until removed. A dirty pool is unsightly and unsanitary.
As a consequence, a great deal of effort has been made to automate the task of pool cleaning. Manual pool cleaners, though generally effective for removing debris from a pool, require a human operator for their operation. Generally, one thinks of a manual pool cleaner as a simple tool having a mesh or a net suspended from a frame which is used in order to mainly sweep or skim debris from the pool. Although inexpensive and simple, cleaning a pool with this tool is rather laborious and cumbersome. Another type of manual pool cleaner features a vacuum head mounted at one end of a long pole. The vacuum head draws water and debris from the bottom or sides of the pool in much the same way that a common household vacuum cleaner removes debris from the floors.
In contrast, automatic pool cleaners operate without human supervision. One conventional automatic pool cleaner has a wheeled carriage equipped with a suction tube for drawing debris from the bottom of the pool into a mesh debris bag. This cleaner also has a tubular supply mast projecting upward from a frame inside the wheel carriage to connect a pressurized water feed line that powers the suction tube and moves the cleaner across the bottom and walls of the pool along a more or less random path. The supply mast also has a horizontal projection upon which a ballast float can be mounted to balance the cleaner. As the cleaner moves over the pool bottom, items of debris are picked up and removed from the pool as the suction tube draws water into the device.
Such automatic cleaners are generally referred to as "pressurized" cleaners. One issue with pool cleaners of this type is that the wheeled carriage may have difficulty traversing the vertical or near-vertical walls of pools. Generally the cleaner will travel about the pool floor and sidewalls until an obstruction is reached, or until it reaches the junction or radius of the floor and sidewall. If the junction is a radius, the cleaner tends to climb up the wall until traction is lost and gravity forces the cleaner to the bottom. Pools may be lined with various types of materials, including tile, cement, plaster, vinyl liner, painted concrete or fiberglass. In cases where the floor/sidewall junction is relatively abrupt, the cleaner may not be able to climb up the wall.
Algae growth on the pool lining material worsens the traction problem for a cleaner in a pool. Once algae grows on a tile surface, for example, the walls become extremely slippery, and the automatic pool cleaner has an extremely difficult time in traversing the walls of the pool.